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The sample, which has been pre-enriched in SSL broth, is suspended in culture medium (OFS agar), incubated and analysed.

Glucose is phosphorylated by the enzyme hexokinase (HK) and adenosine 5'-triphosphate (ATP) to glucose 6-phosphate (G-6-P).

\(\text{Glucose + ATP} \space ^{\underrightarrow{\text{HK}}} \space \text{G-6-P + ADP}\)

In the presence of the enzyme glucose-6-phosphate dehydrogenase (G6P-DH), G-6-P is oxidized by nicotinamide adenine dinucleotide phosphate (NADP⁺) to gluconate-6-phosphate. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is formed:

\(\text{G-6-P + NADP}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{gluconate-6-phosphate + NADP + H}^+\)

The amount of NADPH formed during the reaction is equivalent to the amount of glucose. NADPH is determined based upon its absorbance at 340 nm.

Note:

Alternatively, NAD⁺/NAD + H⁺ can be used instead of NADP⁺/NADP + H⁺:

\(\text{G-6-P + NAD}^+ \space ^{\underrightarrow{\text{G6P-DH}}} \space \text{Gluconate-6-Phosphate + NAD + H}^+\)

The sample is membrane-filtered, incubated and analysed.

In addition to OFS agar and SSL broth, other culture media can be used as an alternative.

The total gas pressure in beer is measured after the beer has been forcefully shaken. The carbon dioxide is then bound through the addition of potassium hydroxide. The amount of air in the beer contributes the remaining volume of gas. Once the value for the total pressure has been corrected by subtracting the quantity of air present in the beer, the carbon dioxide can be measured [1].

Through heating and shaking, the gases contained in beer are collected in a burette filled with potassium hydroxide. The carbon dioxide is bound by potassium hydroxide, and the remaining volume of gas, consisting of oxygen and nitrogen, is measured [1].